Liquid hydrogen-powered aircraft (LH₂ aircraft) offer the potential for a zero-carbon footprint when hydrogen is produced from renewable sources. However, integrating LH₂ aircraft into the air transport system is complex due to differences in LH₂ supply availability and varying levels of airport readiness. To address these disparities and comply with anticipated sustainability regulations, hydrogen tankering can serve as a temporary strategy by carrying additional hydrogen to avoid refueling at destinations lacking LH₂ capabilities. This study presents a novel model that evaluates the potential of tankering while accounting for its interaction with strategic LH₂ infrastructure placement, tactical flight scheduling, and operational aircraft routing. Applying the framework to a real-world case in the Baltic Sea region reveals trade-offs between system costs and environmental benefits under different regulatory measures.

Urban Air Mobility (UAM) systems offer a three-dimensional transportation alternative by using low-altitude airspace, with the potential to reduce travel times and improve access to mobility in regions underserved by current transportation systems. To support efficient design and operation of UAM systems, we develop an integrated optimization framework in response to three interrelated challenges: (i) land use, aeronautical feasibility, community acceptance and other factors that restrict the number of potential locations for vertiports, (ii) bidirectional demand–supply interaction that needs to be considered, as the level of service influences demand for UAM and operators adjust the level of service in response to demand, and (iii) strong interactions between strategic decisions on the distribution of ground infrastructure, tactical decisions on eVTOL fleet size and operational decisions on dispatching and repositioning. Analyzing the decisions in isolation can lead to poor estimates of the overall system performance. The framework consists of (1) a knock-off criteria analysis model for the identification of a realistic set of candidate locations for vertiports, (2) integer programming models in which strategic, tactical and operational decision levels are modeled, and (3) pre-processing techniques to generate near-optimal solutions for real-world instances. By applying the framework in a large-scale real-world setting in the Île-de-France region, we demonstrate complex interactions between strategic, tactical, and operational decision levels and customer demand, revealing various trade-offs between operator profit and traveler generalized travel costs.